Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC: r255977 (partial)

Sweep man pages replacing ad -> ada.

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

mdoc: order prologue macros consistently by Dd/Dt/Os

Although groff_mdoc(7) gives another impression, this is the ordering
most widely used and also required by mdocml/mandoc.

Reviewed by: ru
Approved by: philip, ed (mentors)

Add a geom class to map Linux LVM logical volumes.

The logical disks will appear as /dev/lvm/<vol group>-<logical vol>, for
instance /dev/lvm/vg0-home. G_LINUX_LVM currently supports linear stripes with
segments on multiple physical disks. The metadata is read only, logical
volumes can not be allocated or resized.

Reviewed by: Ivan Voras

Previously known as geom_lvm(4), rename requested by des, phk.